The present invention relates to an operating method for a numerical control unit,    wherein the numerical control unit has access to a sub-program which can be executed by the numerical control unit,    wherein a production machine can be controlled by the numerical control unit by executing the sub-program,    wherein a selection command is predetermined to the numerical control unit by a user by way of a user interface, by means of which at least one program instruction of a sequence of program instructions of the sub-program is selected.
The present invention further relates to a computer program, wherein the computer program comprises machine code which can be immediately executed by a numerical control unit, wherein the machine code is executed by the numerical control unit such that the numerical control unit executes an operating method of this type.
The present invention further relates to a numerical control unit, in which a computer program of this type which can be executed by the numerical control unit is stored.
Numerical control units usually implement a so-called sub-program during operation. The sub-program defines the manner in which position and speed-controlled axes of the production machines (in particular a machine tool) are controlled. Theoretically it is possible to generate the sub-programs directly by way of the user interface of the numerical control unit. The user interface of the numerical control unit nevertheless only makes available the option of setting control commands individually sequentially. In practice the sub-program is therefore generated by means of a CAM system based on data generated by means of a CAD system. The CAM system may comprise a so-called postprocessor.
When the sub-program is generated, a series of sequences of program instructions is generated by a user of the CAM system by means of the CAM system. For each sequence of program instructions, the user of the CAM system specifies to the CAM system a parameterized description of the respective processing. For instance, during milling in mold and die production, the user of the CAM system can predetermine for a finishing operation which tool is to be used, how great a feed depth is to be, what the geometry relationship is and such like. He can also predetermine a path along which a miller is to be moved for instance. On the basis of the parameterized descriptions of the sequences of program instructions, the CAM system then generates the sub-program. The sub-program is transferred to the numerical control unit. It generally no longer contains the parameterized descriptions as such, but instead only the sequence of individual control commands for the position and speed-controlled axes of the production machine. The sequence of the individual control commands may be very long (sometimes several millions of data records). The criteria which form the basis of the determination of the sequence of control commands can no longer be inferred from the sequence of control commands. Examples of such criteria are the line pitch, the tool geometry, the processing strategy, effects of collision prevention calculations, technological values like for instance the situation of the tool etc.
If the sub-program is to be modified, a direct change in the control commands does not as such represent a practicable method, since the criteria forming the basis of the series of control commands can no longer be inferred from the sequence of control commands. Instead, the parameterized descriptions which form the basis of the sequences of program instructions can be changed.
The user of the CAM system is generally a different person from the user of the numerical control unit. In many cases, the user of the CAM system is lacking the technical specifications of the production machine which are to be controlled by means of the sub-program. This may result in the execution of the sub-program by the numerical control unit not resulting in correctly manufactured workpieces. As the ease may be, it may be necessary in cases of this type to fundamentally determine the sub-program again. In many cases, on account of his knowledge of the production machine and its technical specifications it is however apparent to the user of the numerical control unit which technological parameter of which parameterized description has to be changed in order to be able to manufacture a correct workpiece.
Within the prior art, the user of the numerical control unit can only then implement changes to the sub-program if the part of the sub-program to be changed is present in parameterized form in the numerical control unit. This is generally only the case in a small fraction of the overall sub-program. In all other cases, the user of the numerical control unit must communicate with the user of the CAM system and inform the same which parameters in which parameterized description he would have liked to have changed. The user of the CAM system thereupon calls up the CAM system, manually changes the correspondingly parameterized description and then recreates the sub-program. The correspondingly modified sub-program is transferred to the numerical control unit generally as a replacement of the original sub-program.
It may be that the modified sub-program also does not result in the desired result. In a case of this type, the last mentioned procedure, repeatedly in some instances, must be repeated until the workpiece manufactured by means of the sub-program is correct.
The object of the present invention consists in creating possibilities, by means of which the user of the numerical control unit can himself change the CAM-generated sub-program.